The present invention relates to an electromagnetically releasable shutter for a camera.
A camera equipped with an automatic focusing device capable of carrying out a series of actions from the actuation of a focus adjusting member to the completion of exposure by means of a single electromagnet has been proposed in Utility Model Laid-open No. Sho 55-169515.
The above-mentioned automatic focusing device is designed to carry out the following series of operations. An armature lever is actuated by an electromagnet energized upon the operation of a shutter releasing member, to turn a focus adjusting member through a shutter charging member to a position where the lens is in focus and, on the other hand, to release an actuating member in order to turn a diaphragm operating member in a direction to open the diaphragm with a shutter opening member pivotally supported on the actuating member Upon the de-energization of the electromagnet when a time corresponding to the brightness of an object has elapsed after the energization of the electromagnet, the armature lever releases, by its own tendency, the diaphragm operating member from the shutter opening member to allow the diaphragm operating member to turn in the diaphragm closing direction.
However, since this automatic focusing device is designed to release the diaphragm operating member from the shutter opening member directly upon the de-energization of the electromagnet, only by a biasing force acting on the armature lever, the armature lever must be biased by a considerably large resilient force. Therefore, the electromagnet needs to generate a sufficient attractive force to attract the armature lever against a large resilient force, which entails a large power consumption and causes problems that a long rise time is necessary before the effective action of the electromagnet, and thereby the response of the device is delayed.